What did Reformed Calvanist Robert Decker mean by this?

tomana said:

I'm reading a sharing called Pentecostalism: In the Light of the Word, by Robert Decker, a Reformed Calvanist. In this sharing, he says the following with respect to when the Day of Pentecost had come, God poured out His Spirit on at least the apostles (or was it all of the 120 ?) and then Peter stands up to speak to the masses that had gathered :

What happened, Peter explains, is the fulfillment of Joel’s prophecy. The Day of the Lord has come; the New Dispensational day which marks the fulfillment of the Old Testament types and shadows. It’s the Day in which God would call His people out of every nation. And, it’s the Day of judgment that shall be signified by signs and wonders; blood, fire, and vapor of smoke in both heaven and earth; the sun shall be turned to darkness and the moon into blood (compare in this connection Matthew 24 and Revelation 6 where these same signs and wonders are mentioned as marking the Day of the Lord’s return).

what is the connection, regarding the mention of blood, fire, and vapor of smoke in both heaven and earth; the sun shall be turned to darkness and the moon into blood, in Matthew 24 and Rev 6? What is Mr Decker hinting at?

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